1. Field of the Invention
The present invention relates to an electronic device and a control method thereof, and more particularly to an electronic device capable of starting up in a low-temperature environment and a startup method thereof.
2. Related Art
With the improvement of the manufacturing process of electronic elements, electronic devices are becoming light, thin, short, and small. Hence, a user can easily carry the electronic device to a desired place. However, the electronic device does not operate in any environment temperature.
FIGS. 1A and 1B are schematic views of conductivity at various temperatures of a conductor and a semiconductor in the prior art respectively, in which the horizontal axis represents a temperature value, and the vertical axis represents a resistance value. The temperature poses different influences on resistance values of different substances. When an conductor is at a temperature close to the room temperature, a resistance value of a conductor generally is in direct proportion to the temperature. In other words, the higher the temperature is, the larger the resistance value will be:R=R0+aT  Equation 1
where a is a resistance temperature coefficient, and R is the resistance value of the conductor, T is the temperature, R0 is the resistance when the temperature at 0° C.
However, the resistance of an undoped semiconductor decreases when the temperature increases, which are in a geometrical relationship.R=R0ea/T  Equation 2
where a is a resistance temperature coefficient, and R is the resistance value of the conductor, T is the temperature, R0 is the resistance when the temperature at 0° C.
However, variance of a doped semiconductor is more complex. When the temperature rises from the absolute zero, at first, resistance of the semiconductor decreases, and after a great majority of charged particles (electrons or holes/cavities) leave their carriers, the resistance slightly increases with the rising of the temperature due to reduction of activity of the charged particles. When the temperature further rises, the semiconductor generates new carriers (same as the undoped semiconductor), so the original carriers (which are generated due to the doping) become less important, and the resistance decreases once again.
For example, the electronic device includes a circuit loop formed by a plurality of electronic elements. When the electronic elements are driven by a current, the electronic elements generates the signal for processing. However, the activity of the electrons is reduced because of the low-temperature environment (such as an environment below zero degree), so the current cannot be conducted smoothly, and thereby the electronic device operated unsuccessfully. For example, when a startup switch on the electronic device is pressed down, the current drives each electronic element according to layout of the circuit loop. When the current cannot pass through a certain electronic element, startup conditions of the circuit loop cannot be satisfied, so that the electronic device crashes. From a macroscopic point of view, the electronic device gives no response at all, which is the same as crashing; however, from a microscopic point of view, because the current in the electronic device cannot pass through a certain electronic element, or the current passing through the electronic element is too weak, the electronic element cannot be smoothly enabled.
To solve the problem that the electronic device cannot be started up in the low-temperature environment, one method is to add a heating unit (such as a heater) in the electronic device. The heater can increase a temperature within the electronic device, so that each electronic element of the electronic device reaches a required startup temperature. Although the added heating unit can quickly increase the temperature of the electronic device, the heating unit increases the volume of the electronic device. Furthermore, for a manufacturer of the electronic device, the manufacturing cost also increases. Moreover, because power consumption of the heating unit is far higher than that of the electronic elements, power of the electronic device is also consumed at the same time as heating. As a result, the power of the electronic device may be exhausted although the electronic elements reach a temperature at which they can operate.